Various types of recording materials utilizing microcapsules are hitherto known. For example, U.S. Pat. No. 3,219,446 (corresponding to Japanese Patent Publication No. 14344/67) discloses a method, in which a light-sensitive sheet having numerous droplets of a fluid is imagewise exposed to light to thereby immobile the fluid, and the exposed sheet is superposed on an image-receiving sheet, followed by applying pressure all over the sheet to transfer an image corresponding to exposure onto the image-receiving sheet.
Japanese Patent Application (OPI) No. 89915/77 (the term "OPI" used herein means "unexamined published application") discloses a method for obtaining an image in which one component of two-component type heat-sensitive color forming system and a photopolymerizable monomer are encapsulated, and a mixture of another component of the heatsensitive color forming system and the microcapsules is coated on a base to form a light-sensitive sheet, which is imagewise exposed to light to cure the microcapsules in the exposed areas followed by uniformly heating to develop a color on only the unexposed areas.
Japanese Patent Application (OPI) Nos. 124343/82, 179836/82, and 197538/82 disclose an image formation method using microcapsules containing a vinyl compound, a photopolymerization initiator, and a dye precursor, by which a dye image can be obtained by applying pressure all over the material after exposure without requiring heating.
U.S. Pat. No. 3,700,439 (corresponding to Japanese Patent Publication No. 20852/79) discloses an image formation method in which Michler's ketone is encapsulated as a light-sensitive material.
Further, U.S. Pat. No. 3,072,481 discloses a light and pressure-sensitive image formation method, in which a photosensitive substance that easily forms color upon exposure to light when in a dissolved state but is light-insensitive in a solid state is encapsulated, which method comprising imagewise exposing a layer containing the microcapsules and then rupturing the microcapsules to evaporate the solvent.
However, all of the foregoing image formation methods using microcapsules have low sensitivity to light, especially to green light or red light. Furthermore, attempts to increase the sensitivity in these methods are attended by reductions in preservability.
On the other hand, various image formation methods utilizing silver halides as photo-sensor, excluding socalled conventional photographic light-sensitive materials, are known.
For example, British Pat. No. 866,631 discloses a method, in which photopolymerization is directly induced by using a silver halide as a catalyst. According to this method, a product resulting from photolysis of a silver halide is considered to act as a catalyst for polymerization, and high sensitivity as attained by reduction of silver halides through general development processing cannot be obtained.
Belgian Pat. No. 642,477 describes a method which comprises developing exposed silver halide grains with a general developer and inducing polymerization using the resulting silver image or the unreacted silver halide as a catalyst to imagewise form a polymeric compound. However, this method involves complicated operation.
Further, U.S. Pat. No. 3,697,275 (corresponding to Japanese Patent Publication No. 11149/70), U.S. Pat. No. 3,687,667 (corresponding to Japanese Patent Publication No. 20741/72), U.S. Pat. No. 3,746,542 (corresponding to Japanese Patent Application (OPI) No. 10697/74) and Japanese Patent Application (OPI) Nos. 138632/82 and 169143/83 propose a method in which an exposed silver halide is developed with a reducing agent and a coexisting vinyl compound initiates polymerization simultaneously with oxidation of the reducing agent to imagewise form a high-molecular compound. This method, however, requires a development step using a liquid.
However, any of these known image formation methods using silver halides as a photo-sensor has certain disadvantages, such as that high sensitivity cannot be obtained, or complicated development processing procedures are required.